Swimming pool covers are often used for keeping the water free of trash, to shield the water from sunlight that could degrade protective chemicals in the water and for other purposes. Automatic pool covers are often preferable over manually-operated covers, because the cover can be easily extended when the pool is not in use and retracted during use. In most cases, a pool cover box is located at one end of the pool to hold the pool cover system.
Referring to FIG. 1A, an abstract view of a typical pool cover system 10 is shown. System 10 includes a motor 12, a drive shaft 14 extending from motor 12, a wind-up reel 16 for collecting a rope 18, a gear box 20, a swimming pool cover 22 and a roll-up tube 24 on which to wind the cover 22. Rope 18 extends to a remote pulley system (not shown) and then back to a leading edge of the cover 22. Reel 16 and a roll-up tube 24 are usually mounted in a free-wheeling fashion on drive shaft 14 to turn independently therefrom. Gear box 20 includes mechanisms to engage either the reel 16 or the roll-up tube 24, depending on whether the cover 22 is to be extended or retracted.
By turning drive shaft 14 in direction A, clockwise relative to motor 12 as shown, shaft 14 engages the gear mechanism in gear box 20 to drive reel 16 in direction A. This action winds rope 18 on reel 16, thereby causing cover 12 to be extended outward over the pool (not shown). Alternately, by rotating drive shaft 14 in direction B, counter-clockwise relative to motor 12, roll-up tube 24 is engaged by drive shaft 14 via the mechanism in gear box 40, so that the pool cover 22 is retracted on tube 24 and removed from above the pool. The pool cover system 10 shown in FIG. 1A is referred to as a right-hand system, since the pool cover motor is located on the right side in the pool cover box (not shown).
Sometimes the layout of the pool and its surroundings dictate that the pool cover motor be located on the left-hand side of the pool cover box, as shown in FIG. 1B. The pool cover system 30 shown in FIG. 1B is referred to as a left-hand system, since the pool cover motor 32 is situated on the left side of the pool cover box. As in FIG. 1A, the drive shaft 34, reel 36, rope 38, cover 42 and roll-up tube 44 are substantially identical to the corresponding elements shown in FIG. 1A. The main distinction is that different mechanisms are needed in gear box 40, compared to the mechanisms in gear box 20, in order for reel 36 and roll-up tube 44 to be engaged to rotate in directions opposite to the directions of rotation in the right-hand pool cover system shown in FIG. 1A.
Accordingly, in FIG. 1B, if the drive shaft 34 rotates in a direction C, counter-clockwise to motor 32, this action turns reel 16 in direction C to collect the rope 38 on reel 36. Alternately, if drive shaft 34 rotates in a direction D, clockwise to motor 32, then cover 42 is retracted onto roll-up tube 44.
FIG. 2A shows a gear box 20 having a prior art gear mechanism 50 for the right-hand system in FIG. 1A. A single dog gear 52 is fixedly mounted to roll-up tube 24 (shown in FIG. 1A). Another single dog gear 54 is fixedly mounted to reel 16 (shown in FIG. 1A). A double dog gear 56 is rotatably mounted on drive shaft 14 to be free-wheeling along shaft 14. A shear pin 57 is secured into drive shaft 14 to extend orthogonally outward from the drive shaft 14. The shear pin 57 extends into a slanted slot 58 formed in double dog gear 56.
Accordingly, as drive shaft 14 is rotated in direction A, double dog gear 56 is moved along drive shaft 14 in the direction E, so that double dog gear 56 couples single dog gear 54 to drive reel 16 and collect rope 18, shown in FIG. 1A. Alternately, as drive shaft 14 is rotated in direct B, double dog gear 56 is moved along drive shaft 14 in the direction F, engaging single dog gear 52. This action drives the roll-up tube 24 and collects the pool cover 22, shown in FIG. 1A.
Similarly, FIG. 2B shows gear box 40 having a prior art gear mechanism 60 that drives the left-hand system shown in FIG. 1B. A single dog gear 62 engages roll-up tube 44, and a single dog gear 64 engages reel 36. A double dog gear 66 is mounted to free-wheel on drive shaft 34. When drive shaft 34 rotates in direction C, double dog gear 66 is forced by shear pin 67 along shaft 34 in direction H. This engages the reel 36 to collect the rope 38, shown in FIG. 1B. When drive shaft 14 rotates in direction D, double dog gear 66 is forced by shear pin 67 along shaft 34 in direction G. This engages the roll-up tube 44 to retract cover 42, as shown in FIG. 2B.
Accordingly, prior art systems involve a swimming pool builder using both right-hand and left-hand motor systems, including different gear boxes, in order to work with various pool layouts and the requirements of customers. Consequently, both right-hand and left-hand types of motor systems must be readily supplied by a pool equipment supplier, adding to the supplier's inventory demands. Moreover, it is difficult to forecast which type of system will be in greater demand, resulting in over-supply and under-supply of right and left-hand motor systems. Furthermore, complex prior art gear boxes, such as shown in FIGS. 2A and 2B, are relatively expensive and are maintenance-intensive.
A pool cover motor system may also be equipped with a torque limiter separately mounted, so that, in the event the cover or one of its components becomes jammed or stuck, the motor or other parts of the pool cover motor system will not be damaged. Typically, torque limiter apparatus includes some type of device that slips relative to the rotatable shaft in the event that a predetermined torque limit on the device is exceeded. However, adding a torque limiter to the motor system also adds extra cost to the manufacture of the motor system.